Historical manure application affects accumulation pattern of residue-derived carbon via promoting macro-aggregation in Andosols, Japan

Managing post-harvest crop residues is key to maintaining soil organic carbon (SOC) for achieving sustainable agriculture and mitigating climate change. However, how historical land management and residue quality affect residue-derived carbon (C) accumulation and pattern through aggregate formation and stabilization remains unclear, especially in Andosols. We conducted a 450-day in-situ incubation experiment using 13 C-labeled maize residues (leaf: C/ N = 15; root: C/ N = 30) at historical managed cropland (Andosols) in Tokyo, Japan, under three land managements—manure (M), chemical fertilizer (Cf), and no fertilizer (Nf). Soil samples collected at 20, 60, 120, and 450 days were fractionated into macroaggregates (>250 μm), microaggregates (53–250 μm), and the silt+clay fraction (<53 μm) and analyzed. After 450 days, the remaining proportions of residue-derived C were 23 % (leaf) and 29 % (root), with no significant differences among land managements. However, decomposition rates at 450 days estimated by two-pool first-order model were significantly lower in M (0.37 mg C kg −1 day −1 ) than in Cf (0.60), indicating that manure application affected the accumulation pattern of residue-derived C. Because the macroaggregate mass proportion was higher in M (82 %) than in Cf (70 %), historical manure application should promote the macroaggregate formation and enhance the physical protection of residue-derived C, resulting in higher residue-derived C in macroaggregates at 450 days in M (0.38 g C kg −1 ) than in Cf (0.29). Overall, historical manure application caused the different accumulation pattern of residue-derived C especially at later period via macro-aggregation in Andosols, Japan.